The aeson-pretty package

A JSON pretty-printing library compatible with aeson as well as
a command-line tool to improve readabilty of streams of JSON data.

The library provides the function encodePretty. It is a drop-in
replacement for aeson's encode function, producing JSON-ByteStrings for
human readers.

The command-line tool reads JSON from stdin and writes prettified JSON
to stdout. It also offers a complementary compact-mode, essentially the
opposite of pretty-printing. If you specify -flib-only like this